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RECENT PROGRESS IN PHYSICS.¢ 
By Prot. Sit J.J. LHOmsons MeoAS Ii Ds Ds Se. sky Resi 
It has usually been the practice of the president of this association 
to give some account of the progress made in the last few years in 
the branch of science which he has the honor to represent. 
I propose this evening to follow that precedent and to attempt to 
give a very short account of some of the more recent developments 
of physics, and the new conceptions of physical processes to which 
they have led. 
The period which has elapsed since the association last met in 
Canada has been one of almost unparalleled activity in many 
branches of physics, and many new and unsuspected properties of 
matter and electricity have been discovered. The history of this 
period affords a remarkable illustration of the effect which may be 
produced by a single discovery; for it is, I think, to the discovery of 
the Réntgen rays that we owe the rapidity of the progress which has 
recently been made in physics. <A striking discovery like that of the 
Rontgen rays acts much like the discovery of gold in a sparsely popu- 
lated country; it attracts workers who come in the first place for the 
gold, but who may find that the country has other products, other 
charms, perhaps even more valuable than the gold itself. The coun- 
try in which the gold was discovered in the case of the R6ntgen rays 
was the department of physics dealing with the discharge of electric- 
ity through gases, a subject which, almost from the beginning of elec- 
trical science, had attracted a few enthusiastic workers, who felt 
convinced that the key to unlock the secret of electricity was to be 
found in a vacuum tube. Réntgen, in 1895, showed that when elec- 
tricity passed through such a tube, the tube emitted rays which could 
pass through bodies opaque to ordinary light; which could, for ex- 
ample, pass through the flesh of the body and throw a shadow of 
the bones on a suitable screen. The fascination of this discovery 
attracted many workers to the subject of the discharge of electricity 
«Presidential address at British Association meeting, 1909. Reprinted by 
permission (omitting introduction) from Chemical News, London, vol. 100, No. 
2596, August 27, 1909. 
185 
